var websocket = null;  
var username = localStorage.getItem("name");  
  
//判断当前浏览器是否支持WebSocket  
if ('WebSocket' in window) {  
    websocket = new WebSocket("ws://" + document.location.host + "/JosephWeb/websocket/" + username + "/"+ _img);  
} else {  
    alert('当前浏览器 Not support websocket')  
}  
  
//连接发生错误的回调方法  
websocket.onerror = function() {  
    setMessageInnerHTML("WebSocket连接发生错误");  
};  
  
//连接成功建立的回调方法  
websocket.onopen = function() {  
    setMessageInnerHTML("WebSocket连接成功");  
}  
  
//接收到消息的回调方法  
websocket.onmessage = function(event) {  
    setMessageInnerHTML(event.data);  
}  
  
//连接关闭的回调方法  
websocket.onclose = function() {  
    setMessageInnerHTML("WebSocket连接关闭");  
}  
  
//监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。  
window.onbeforeunload = function() {  
    closeWebSocket();  
}  
  
//关闭WebSocket连接  
function closeWebSocket() {  
    websocket.close();  
}  